Method and apparatus for harvesting crops

ABSTRACT

A method and system of harvesting crops involves cutting and threshing the crop, separating graff (a mixture of grain kernels, chaff, weed seeds, and other organic matter) from straw (plant stalks), and returning the straw to the field. This is preferably carried out in a harvesting unit of the pull type having a graff storage tank. The collected graff is moved to a stationary cleaning mill in a different location by means of a suitable vehicle such as a truck. Storage of the graff prior to cleaning is avoided and the cleaning mill, and preferably the harvesting unit and vehicle, are designed to make this possible. This avoids difficulties caused by the poor material flow of graff. Various details of the equipment are also novel.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to the harvesting of grain and seed cropsof the kind that are conventionally harvested by means of a combineharvester. More particularly, the invention relates to systems, methodsand apparatus for harvesting such crops.

[0003] 2. Description of the Prior Art

[0004] The applicant herein has already disclosed a novel method of andapparatus for harvesting grain and seed crops that provide analternative to the use of conventional combine harvesters. In thisregard, reference is made to U.S. Pat. No. 5,794,423 issued on Aug. 18,1998; U.S. Pat. No. 5,795,222 issued on Aug. 18, 1998; and U.S. Pat. No.5,873,226 issued on Feb. 23, 1999; all of these patents having beenassigned to McLeod Harvest Inc. and are referred to collectively in thefollowing description as “the McLeod patents.”

[0005] A conventional combine harvester operates by carrying out all ofthe harvesting steps in the field on a continuous basis. The crop plantsare cut, the cut plants are threshed to separate grain (or seeds such aspeas, etc.), chaff and (inevitably) weed seeds fiom the stalks, thegrain is then cleaned by separating it from the chaff and weed seeds,the grain is delivered to a waiting collection vehicle, and the stalks,chaff and weed seeds are returned to the field. The disadvantages ofthis are that (a) combine harvesters are very expensive to purchase andto operate; (b) they are not very efficient at cleaning the grain, sosome grain is lost and/or further grain cleaning is required; and (c)chaff and weed seeds are returned to the field, so that their economicvalue is lost and weeds proliferate.

[0006] The concept underlying the systems disclosed in the above patentsis that, instead of attempting to carry out all of the harvesting stepsin the field, only the step of threshing and removing stalks is carriedout, and the remaining product (a mixture of grain, chaff and weedseeds—referred to by the coined word “graff”) is collected andtransported to a fixed grain cleaning site. The advantage of this isthat the harvesting equipment may be less complicated and expensive thana conventional combine harvester, the cleaning of the grain may becarried out more efficiently at a fixed site, the economic value of thechaff and weed seeds may be realized, and the need for herbicides isreduced (because the weed seeds are collected rather than being returnedto the field).

[0007] It has been found that this system is extremely effective, butinconveniences have been encountered in that graff has proven to be adifficult material to handle and process. Since graff contains a largepercentage of chaff, it is bulky for its weight and it is quite fibrousin composition. Unlike grain collected by a combine harvester, graffdoes not easily “flow” from containers and it is difficult to move byconventional means, such as augers, because it bridges or binds withinitself and does not flow internally to replace material that has beenremoved from the bottom of a container or pile of the material. Ingeneral, it can be said that graff tends to pack, clump, bridge,rat-hole and bind, rather than flow smoothly. This causes problems notonly when the graff is stored in silos or the like before it isprocessed, but also causes difficulties of material flow within theharvesting device and transportation vehicles.

[0008] Moreover, graff is difficult to store because, if stored in theopen, it tends to blow away and also to spoil if it gets wet. However,if stored in a container, it is difficult to remove for the reasonsmentioned above.

[0009] Additionally, there is a need to improve the overall efficiencyof the system generally and to improve the manner in which individualcomponents operate in order to increase the economic competitiveness ofthe system with conventional harvesting systems.

SUMMARY OF THE INVENTION

[0010] An object of the invention is to improve the efficiency and toreduce the equipment cost of carrying out a grain harvesting method ofthe type disclosed in the patents mentioned above.

[0011] Another object of the invention, at least in its preferred forms,is to overcome difficulties caused by the poor flow properties of graff.

[0012] Another object of the invention, at least in broader aspects, isto optimize a grain harvesting system as opposed to a single grainharvesting machine such as a conventional combine harvester.

[0013] Another object of the invention is to reduce the operational costof carrying out a grain harvesting method of the type disclosed in thepatents mentioned above.

[0014] Another object of the invention, at least in its preferred forms,is to improve the effectiveness of the harvesting unit used to separatethe graff from the crop stalks in the field.

[0015] Another object of the invention, at least in its preferred forms,is to improve the effectiveness of the grain cleaning mill used toseparate grain from the remainder of the graff at a fixed site and toprocess crop the residue.

[0016] According to one aspect of the invention, there is provided amethod of harvesting and cleaning a plant crop, wherein the crop is cutfrom a field area and threshed in a mobile harvesting unit to producestalks that are returned to the field area and “graff”, a mixtureincluding grain, chaff and weed seeds, which is collected within theharvesting unit; the collected graff is transferred periodically fromthe harvesting unit to at least one vehicle and transported by said atleast one vehicle to a cleaning mill, and the graff is cleaned by thecleaning mill to produce a cleaned grain product and “millings”, amixture including chaff and weed seeds. To avoid problems caused by thepoor flow characteristics and very low density of graff, the method isoperated to avoid storage of the graff prior to cleaning by the cleaningmill.

[0017] What we mean by avoiding storage of the graff prior to cleaningis that the graff is not transferred to any temporary storage containeror storage pile from the time it is produced by the harvester to thetime it is cleaned by the cleaning mill. The graff is held only in theharvester unit and the vehicle, and is fed immediately into the cleaningmill. Consequently, the use of stationary surge bins and the like at thecleaning mill or other area is specifically avoided. The graff is feddirectly from the harvesting unit to the vehicle, and directly from thevehicle to the a receiving unit for the cleaning mill from which it isfed substantially immediately and completely into the cleaning mill.

[0018] Thus, according to another aspect of the present invention, thereis provided a system for harvesting and cleaning a plant crop, whichincludes a harvesting unit for cutting a crop from a field area and forthreshing the cut crop to produce stalks that are returned to the fieldarea and “graff”, a mixture including grain, chaff and weed seeds, whichis collected within the harvesting unit; at least one vehicle forreceiving collected graff from the harvester unit when the harvestingunit is at least partially full, and for transporting the graff to acleaning mill; and a cleaning mill located at a site (yard area) remotefrom the field area, for cleaning the graff to produce a cleaned grainproduct and “millings”, a mixture containing chaff and weed seeds. Thesystem specifically excludes and avoids the use of any device forstorage of the graff prior to cleaning of the graff in the cleaningmill.

[0019] According to another aspect of the invention, there is provided astationary cleaning mill for graff, comprising an entrance (usuallylocated at an elevated position) for the graff, screening apparatus forseparating grain from the graff to produce cleaned grain and millings,and separate outlets for the cleaned grain and millings. The cleaningmill includes a receiving unit for the graff for feeding the graff tothe entrance of the graff cleaning mill, the receiving unit being sizedto permit a graff delivery vehicle to drive into the receiving unit totransfer an entire vehicle load of graff to the receiving unit by adirect dumping operation of the entire vehicle load.

[0020] In another aspect, the invention provides a stationary cleaningmill for graft, comprising an entrance (usually located an elevatedposition) for the graff, screening apparatus for separating grain fromthe graff to produce cleaned grain and millings, and separate outletsfor the cleaned grain and millings. The cleaning mill includes amaterial-conveying fan at the outlet for the millings, thematerial-conveying fan impacting the millings to cause at least partialcrushing or breaking of weed seeds in the millings, removing themillings from the cleaning mill, and propelling the millings through theoutlet for the millings.

[0021] According to yet another aspect of the invention, there isprovided a mobile harvesting unit for harvesting graft, including awheeled harvester body and a harvesting header at the front of theharvester body for cutting a crop from a field area, the harvester bodycontaining a threshing unit for the cut crop for separating stalks fromgraff, a discharge for discharging separated stalks back to the fieldarea, and a storage tank for storage of the separated graff. Theharvesting unit includes an elongated hitching arm having oppositelateral ends for connection at one end to the harvester body and at anopposite end to a rear portion of a propulsion device, the hitching armhaving a raised section intermediate the opposite ends passing over andclear of the harvesting header.

[0022] According to yet another aspect of the invention, there isprovided a hitching arm for a graff harvester, comprising a rigidelongated element having two opposite ends for connection, respectively,to the graff harvester and to a propulsion device. The arm has upwardlyextending sections extending from each opposite end towards a centre ofthe hitching arm, and an elevated centre section.

[0023] According to still another aspect of the invention, there isprovided a receiving unit for graft, for feeding graff to an elevatedentrance of a graff cleaning mill, including a receptacle for graff anda conveyor for raising graff from the receptacle to the elevatedentrance. The receptacle is sized to permit a graff delivery vehicle todrive into the receptacle and to deposit an entire vehicle load of graffinto the receptacle by a direct dumping operation.

[0024] Preferably, the invention may provide a method of harvesting andcleaning a plant crop, wherein the crop is cut from a field area andthreshed in a mobile harvesting unit to produce stalks that are returnedto the field area and graft, a mixture of threshed grain kernels, chaffand weed seeds, which is collected within the harvesting unit, thecollected graff is transferred to a vehicle when the harvesting unit isfull, the graff is transported by the vehicle to a cleaning mill locatedin a yard area remote from the field area, and the graff is cleanedautomatically by the cleaning mill to produce a cleaned grain productand a mixture of chaff and weed seeds, wherein a capacity of theharvesting unit to hold graff is made the same as or smaller than acapacity of a vehicle used for the delivery, the rate of cleaning of thegraff by the cleaning mill is made the same as or higher than a rate ofgraff output from the field area averaged over several cycles of fillingand emptying the harvesting unit and transfer to the vehicle, and thenumber and speed of operation of the vehicles is made high enough toavoid substantial waiting periods between filling of the harvesting unitwith graff and transfer of the collected graff to the vehicle.

[0025] Preferably, the capacity of the harvesting unit is substantiallythe same as the capacity of the vehicle, and a single vehicle isprovided for transporting the graff.

[0026] It is also preferable that the capacity of the cleaning mill tohold and process graff is no less than the capacity of the vehicle totransport graff from the field area to the cleaning mill, and the rateof cleaning of the graff by the cleaning mill is about the same as therate of graff output from the field area.

[0027] In another preferred form, the invention provides a system ofharvesting and cleaning a plant crop, which comprises: a harvesting unitfor cutting a crop from a field area and threshing the cut crop toproduce stalks that are returned to the field area and “graff”, amixture of grain, chaff and weed seeds, which is collected within theharvesting unit, a vehicle for receiving collected graff from theharvester unit when the harvesting unit is full, and for transportingthe graff to a cleaning mill; and a cleaning mill located in a yard arearemote from the field area, for cleaning the graff to produce a cleanedgrain product and “millings”, a mixture of chaff and weed seeds, whereina capacity of the harvesting unit to hold graff is made the same as orsmaller than a capacity of a vehicle used for the delivery, a rate ofcleaning of the graff by the cleaning mill is made the same as or higherthan a rate of graff output from the field area averaged over severalcycles of filling and emptying the harvesting unit and transfer to thevehicle, and a number and speed of operation of the vehicles is madehigh enough to avoid substantial waiting periods between filling of theharvesting unit with graff and transfer of the collected graff to thevehicle.

[0028] In another preferred aspect, the invention relates to a mobileharvesting unit for harvesting graff, comprising a harvesting header(e.g. a direct-cut or swath pick-up type) at a front of the harvestingunit for removing a crop from a field area, a threshing unit forseparating stalks from a mixture graff, a mixture of grain, chaff andweed seeds, a storage tank for storage of the separated graft, and ahitching arm for connection to a rear portion of a propulsion device,the hitching arm being of inverted generally U-shape to allow attachmentat opposite ends of the arm to the unit and the propulsion device whileextending over the harvesting header.

[0029] In the harvesting unit of this kind, the hitching arm preferablysupports and guides a mechanical driveling for transferring mechanicalpower from the propulsion device to the harvesting unit, the drivelineincluding a plurality of rotary shafts joined by constant velocityjoints or U-joints to allow the driveline to adapt to changes ofdirection of the hitching arm. The hitching arm may also be used forguiding and protecting hydraulic tubes for conveying hydraulic fluidunder pressure from the propulsion device to the harvesting unit. Thesetubes may pass through an interior channel in the hitching arm.

[0030] In another preferred aspect, the invention relates to a mobileharvesting unit for harvesting graff, comprising a cutting head, athreshing unit for separating stalks from graft, a mixture of grain,chaff and weed seeds, a storage tank positioned above the threshing unitfor temporarily storing graff, an auger bed for transporting graff tocollection areas on opposite lateral sides of the unit, and a pair ofgraff elevators, one on each side of the storage tank, forsimultaneously removing graff from the collection areas of the auger bedand for delivering removed graff to a top of the storage tank.

[0031] Further, the invention in another preferred aspect relates to acleaning mill for graff, comprising a receiving unit for graff sized toallow a graff transportation vehicle to drive at least partially thereinfor dumping a load of graff, a graff conveyor for feeding graff into themill as a moving matted layer of approximately constant thickness(preferably in the range of 1.5 to 3 inches), and elevators for tiltingthe receiving unit, following removal of the vehicle, to cause the loadof graff to slide to the graff conveyor.

[0032] Further, in another preferred aspect, the invention relate to acleaning mill for graff, comprising an aspirator for blowing air througha falling matted layer of graff to remove chaff and light materialsleaving aspirated graff containing grain kernels and heavy materials, acentrifugal separator for removing the chaff from the air after passingthrough the curtain of graff, a fan and ductwork for recirculating aircontinually through the curtain of graff and through the separator, ascreening unit for separating grain from remaining materials from theaspirated graff, an outlet for the separated grain, a mill for millingthe remaining materials to produce millings, ductwork for circulatingthe millings to the centrifugal separator, an outlet device for removingsolids from the centrifugal separator for discharge from the mill.

[0033] It will be appreciated that, in the following discussion, thereference to “grain kernels” or “grain” as the desired product of theharvesting operation should be taken to include the grain kernels orseeds of all crops that are harvestable by conventional combineharvesters, not merely wheat. Such products include, for example, oats,barley, peas, lentils, rice, soybeans, mustard seed, canola, rapeseed,etc. The harvesting system of the present invention can be operated withall such crops.

[0034] Moreover, while the grain kernels are separated from the graff toleave a mixture of chaff, weed seeds and other materials, referred to asmillings, the components of the millings may themselves, if desired, beseparated either during the cleaning of the grain in the cleaning mill,or subsequently. Separate outlets may be provided for the separatecomponents of the millings. Thus, while the claims of this applicationmay refer to an outlet for millings, there may in practice be two ormore outlets for various components of the millings, and the term usedin the claims is intended to cover this eventuality.

[0035] It will also be understood that the millings may containadditional elements such as unthreshed heads, pieces of straw, dust,leaves, and other harvesting residues and debris, and so the term shouldnot be limited merely to a mixture of weed seeds and chaff.

[0036] In the following description, numerical values are oftenexpressed both in metric units and in non-metric units (the latter beingshown in brackets). In the event of any discrepancy, the valuesexpressed in non-metric units should be considered correct.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037]FIG. 1 is a schematic sketch illustrating the overall harvestingmethod according to a preferred form of the present invention;

[0038]FIG. 2 is a perspective view of a preferred embodiment of aharvesting unit suitable for use in the method of the invention;

[0039]FIG. 3 is side view, with internal elements visualized, of thepreferred harvesting unit of FIG. 2;

[0040]FIG. 3A is a view similar to FIG. 3, showing the threshingmechanism and graff collection area in isolation;

[0041]FIG. 4 is a side view in cross-section of a bitching arm of theharvesting unit of FIGS. 2 and 3;

[0042]FIG. 5 is a top plan view of a harvesting unit according to FIG. 2and FIG. 3 showing the method of attachment to a conventional tractor;

[0043]FIG. 6 is a top plan view of an auger bed, shown in isolation fromother equipment, as used in the harvesting unit of FIG. 2 and FIG. 3;

[0044]FIG. 7A, 7B, 7C and 7D are simplified cross-sectional view of theharvesting unit of FIG. 2 and FIG. 3, showing how graff is lifted intoand moved within the graff storage tank;

[0045]FIG. 8 is a side elevation of an alternative preferred embodimentsof the harvesting unit and hitching arm of the present inventionattached to a conventional tractor;

[0046]FIG. 8A is an enlarged view, partly in cross-section, of a jointin a power transmission line carried by the hitching arm of FIG. 8;

[0047]FIG. 8B is a top plan view of the harvester of FIG. 8 showing ahorizontal section immediately beneath the graff storage tank and strawwalkers, showing the augers used to move the graff and the direction ofgraff flow (indicated by arrows);

[0048]FIG. 8C is a top plan view of the harvesting unit of FIG. 8looking down upon the graff collection tank and showing (by arrows) thedirection of movement of graff through the tank and removal chute;

[0049]FIG. 9 is a perspective view of a preferred embodiment of acleaning mill suitable for use in the method illustrated in FIG. 1;

[0050]FIG. 10 is a perspective view on an enlarged scale of a screeningunit forming part of the cleaning mill of FIG. 9;

[0051]FIG. 11 is a side elevation of a graff receiving unit and graffconveyor, on an enlarged scale, forming part of the cleaning mill ofFIG. 9, the receiving unit being in the down position ready to receive agraff transportation vehicle;

[0052]FIG. 12 is a view similar to FIG. 11, but showing the receivingunit in the raised position for feeding graff to the graff conveyor;

[0053]FIG. 13A is a side elevational view of the aspirator, fan andcentrifugal separator forming a closed graff cleaning circuit andforming part of the apparatus of FIG. 9;

[0054]FIG. 13B is a view similar to that of FIG. 13A from the otherside;

[0055]FIG. 13C is a perspective view of a reel used in the apparatus ofFIGS. 13A and FIG. 13B;

[0056]FIG. 13D is a sketch showing a millings discharge pipe having acyclone deceleration unit at its free end; and

[0057]FIG. 14 is a side elevation of a cleaning mill, graff receivingunit and graff conveyor according to a second preferred embodiment ofthe present invention showing the graff receiving unit in an uprightposition containing a transported load of graff; and

[0058]FIG. 15 is a top plan view of the cleaning mill (the graffreceiving unit and graff conveyor having been omitted) according to FIG.14.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Harvesting Method

[0059] One of the objectives underlying the present invention is toimprove the efficiency of the graff harvesting and cleaning systemdescribed in the McLeod patents mentioned above, as well as providing afurther alternative to the use of conventional combine harvesters forharvesting grain. The inventors named in the present application hasfound that one way of achieving this is to ensure that components of thesystem are designed so that harvested material (the graff) flowsconstantly and efficiently through the system without avoidable delays.This has the advantage not only of maximizing operation efficiency, butalso of avoiding the need for temporary storage of graff and thusavoiding the problems caused by the poor flow properties of graff.

[0060] As in the McLeod patents, the components of the system of thepresent invention comprise: (1) a mobile harvesting unit for harvestingthe crop, i.e. for collecting graff and returning stalks to the field;(2) a cleaning mill for separating grain kernels from the remainder ofthe graff, and preferably for crushing and/or shredding the remainder ofthe graff to compact it and to reduce the viability of the weed seeds;and (3) one or more vehicles (normally trucks provided with open truckboxes coverable by a tarpaulin or the like to prevent loss of graffthrough blowing) for transporting harvested graff from the harvestingunit to the cleaning mill.

[0061] As already noted, a particular problem encountered in dealingwith graff is that, while it is not particularly heavy, it is very bulkycompared to the cleaned grain product delivered from a conventionalcombine harvester (the amount of graff collected from a given crop areamay be as much as four times higher in terms of volume than the amountof grain collected by a combine harvester from the same crop area).Moreover, unlike grain, graff does not flow easily; it tends to pack,clump, bridge, rat-hole and bind, making its transfer within and betweenmechanical equipment very difficult.

[0062] In view of the problem of excessive bulk, one might think that asolution would be to provide a harvesting unit with an internal graffcollection container (storage tank) that is as large as possible toavoid the need for frequent stops to discharge the collected graff.However, if this is done, the volume of the collected graff may exceedthe capacity of the transport vehicle (truck) used to transport thegraff to the cleaning mill, resulting in delays and/or the need foradditional vehicles. Similarly, if the amount of graff delivered to thecleaning mill at one time is too large, there may be a build-up oroverflow of collected unprocessed graff, ultimately resulting in atemporary storage or termination of harvesting to allow for the graffbuild-up to be processed.

[0063] A preferred solution to this problem is to ensure that thecapacities of the various components (harvesting unit, vehicle, cleaningmill) are matched to allow an even and continuous flow of graff throughthe system to avoid the need for temporary storage of the graff beforeit is processed. Consequently, the graff-holding capacity of theharvesting unit should preferably be as large as possible, but no largerthan the capacity of a vehicle used to transport the graff to thecleaning mill, and the throughput of the cleaning mill should preferablybe such that it may handle a volume of graff at least as great as thegraff holding capacity of a vehicle used to transport the graff in thevehicle turnaround time (the time between successive deliveries of grafffrom the harvesting unit to the cleaning mill).

[0064] This is illustrated schematically in FIG. 1 of the accompanyingdrawings. The drawing is a plan view representing in a very general waya field area 10, a road (or track) system 11 and a yard area 12. Aharvesting unit 15 (graff harvester), pulled by a conventional tractor16, harvests a crop from the field area 10, returns stalks to the landand collects graff (threshed grain kernels, chaff, weed seeds, smallbits of straw, etc.) inside the harvesting unit 15 in an internalcontainer (storage tank) until the container is full. The harvestingunit 15 then stops and unloads the collected graff into a grafftransport vehicle 17 (generally a standard dump truck with anopen-topped truck box and an openable rear silage gate) which, whenfull, transports the collected graff 18 to a cleaning mill 20 located inthe yard area 12. Here, the vehicle 17 dumps the graff 18 through theentire rear gate into a graff receiving unit 21 of the cleaning mill 20and returns (as shown at 17′) to the field area to repeat the cycle. Thecapacity of the graff receiving unit 21 should be at least as large asthe carrying capacity of the vehicle 17 so that the vehicle may unloadfully immediately upon arrival at the cleaning mill so that it is notdelayed. If the cleaning mill 20 is intended to process the graff fromseveral harvester units at the same time, then the capacity of thecleaning mill must be increased correspondingly. The graff 18 depositedin the receiving unit 21 of the cleaning mill passes immediately throughthe cleaning mill and is separated into cleaned grain 25 and millings 26(a mixture of smaller grain kernels, weed seeds, chaff, and small bitsof straw, etc.) that have been subjected to milling.

[0065] The harvesting unit 15 has an internal graff storage capacitythat should be approximately the same as, or at least no larger than,the capacity of the vehicle 17 so that the internal container of theharvesting unit, when full, may be emptied completely into the truck boxof a single vehicle 17. This may be done by stopping the harvesting unitat a waiting truck, or by emptying the harvesting unit into a movingtruck as both continue to move (with or without further harvesting).More than one vehicle may be provided, depending on the distance of thefield area 10 from the yard area 12, and the rate of operation of theharvesting unit 15. Ideally, there should be a waiting vehicle 17whenever the harvesting unit 15 is filled and is consequently requiredto stop. For greatest economy of operation, only a single vehicle 17 isrequired to operate the method continuously, which means that the timerequired to fill the container of the harvesting unit with harvestedgraff should be approximately the same as the time for transport,dumping and return of the single vehicle 17.

[0066] This may be expressed in another way. Although the harvestingunit 15 harvests (collects and delivers) the graff on a batch basis, itwill, on average, have a rate of graff delivery that can be expressed inunits of weight or volume per unit time. The rate of graff harvesting bythe harvesting unit 15 should, for the most effective and efficientoperation, be essentially the same as the average rate of transport ofthe graff by the vehicle 17 from the field area 10 to the yard area 12.

[0067] At the yard area 12, the cleaning mill 20 is capable ofprocessing graff at a certain speed when operating continuously. Thiscan also be expressed in terms of units of weight or volume per unittime. For efficient and effective operation, the speed of processing ofthe graff should be no slower than the average rate of graff delivery bythe vehicle 17, and no slower than the rate of graff harvesting by theharvesting unit 15. This ensures that the various pieces of equipment(harvesting unit, cleaning mill and delivery trucks) all work as anintegrated system.

[0068] Ideally, therefore, in this system, the rate limiting step shouldbe the harvesting of the crop by the harvesting unit 15. That is to say,the crop should be collected, transported and processed as quickly asthe crop can be cut and threshed (stalks removed) by the harvesting unit15. This means that, if the field area 10 is physically close to theyard area 12, it may be adequate to have a single vehicle 17 because itmay have the time to transport, dump and return between each completionof a filling cycle of the harvesting unit. This is the ideal situation.Obviously, from time to time, the ideal arrangement will break down, butthe system should be designed to allow such efficient operation to bethe norm. As the distance from the field area to the yard areaincreases, more vehicles may be provided. However, as the separation ofthe field area from the yard area increases, there will come a time whenit is too expensive or impossible to provide enough vehicles 17 tomaintain the required minimum rate of collection and delivery of thegraff. Often this physical separation limit is found to be in the orderof 6 km. On the other hand, the physical separation of the field area 10and the yard area 12 should have no significant effect on the speed ofthroughput of the cleaning mill because this should always be the sameas, or higher than, the rate of crop cutting and graff collection by theharvesting unit, or several harvesting units if the mill is intended toservice several such units. The relative capacities and throughputs ofthe harvesting unit 15, the vehicle(s) 17 and the mill 20 should bedesigned and utilized to ensure that this is so. Trucks of the typenormally employed for hauling grain and the like usually have a capacityof about 21 m³ (750 cubic feet), so the storage capacity of theharvesting unit 15 and the capacity of the graff receiving unit 21should preferably be about the same.

[0069] While this optional organization of the entire system isdesirable, it would still provide problems if carried out with equipmentbasically as shown in the McLeod patents. The reason for this is bestdescribed with reference to FIG. 7 of U.S. Pat. No. 5,795,222, which isone of the McLeod patents. This drawing shows a grain truck 20 havingraised sides 21 discharging graff into a hopper 23 through a smalldischarge port provided at the lower central part of the read raisedside of the truck. The hopper is then emptied by a large grain auger 22into one of several surge storage bins 24 provided for temporarystorage. A further auger 26 then transfers graff at a constant rate fromone of the bins 24 to the upper entrance 54 of the yard plant (cleaningmill) 48. However, because of the poor flow properties of the graff, itis difficult to discharge the material from the truck through the smalldischarge port in the rear tailgate of the truck, and difficult to getthe graff to flow from the lower conical ends of the surge storage bins.This creates inefficiencies and difficulties that can cause delays inthe cleaning of the graff while attempts are made to cause the graff toflow properly again.

[0070] Solutions to this problem, at least in its most preferred formsof the present invention, make use of ways of causing graff to flow thathave been devised by the inventors. The inventors have observed thatgraff can be caused to flow without difficulty in the following ways:

[0071] 1) Graff can be caused to slide bodily or tumble down a slope (orchute) inclined at a suitable downward angle, provided that it is notimpeded in any way, e.g. by inwardly tapering or inwardly stepped wallsprovided at the lateral sides of the sloped surface or chute. Thisavoids the problem encountered when a delivery truck of the type shownin the McLeod patents is provided, i.e. a truck having a small openingor delivery port provided in the tailgate (which is typical of graindelivery trucks). The tailgate impedes the sliding or tumbling action ofthe graff and provides a “choke point” that impedes smooth graff flow.

[0072] 2) A quantity of graff can be removed from the bottom of a pileof graff, or a container (e.g. a silo) full of graff, provided thatessentially the entire lowermost layer (or an inner layer) of the graffis removed all at one time, rather than just a part of the graff fromthe lowermost layer (or any inner layer) as has been doneconventionally. This can be achieved by moving a conveyor surface or aseries of elongated transverse elements (rakes or slats) beneath thepile or contained body of graft, while preferably maintaining theremainder of the body of graff essentially stationary in some way. Ifessentially the entire lowermost layer of the graff is removed, theremainder of the graff can move downwardly without binding or bridging.If it is desirable to prevent the remainder of the graff from moving asthe lowermost layer is withdrawn (which is the case if a constant supplyof graff is to be delivered to a piece of equipment, such as thecleaning mill), the remainder of the graff may be confined within acontainer or behind a retaining wall, or the body of graff may besupported on an upwardly sloping surface so that the weight of the bodyof graff prevents it from following the movement of the removed layer.

[0073] 3) Graff can be caused or “encouraged” to flow bodily from onepoint A, e.g. a point of delivery within a container, to another point Bby moving an upper layer of a body of graff from point A towards pointB. This is best used in conjunction with 2), i.e. the moving of a lowerlayer of material from point A to point B (without of course attemptingto prevent the movement of the body of graff as is done in some forms of2). This can be done, for example, by providing augers at an upper levelof the body of graff, and is particularly useful within a graffharvesting unit where graff is collected a the front of a container andhas to be moved to an outlet region or well at the back of thecontainer.

[0074] 4) Graff can be conveyed in a current of air of suitable volumeand velocity, but this may cause some separation of the components ofthe graff. However, such separation is desired in certain parts of thesystem, e.g. in the cleaning mill, so movement of graff in this waytends to be confined to such system parts.

[0075] 5) Graff can, of course, be moved bodily as a single mass, e.g.on a horizontal moving surface (e.g. a conveyor). This is useful, forexample, for emptying graff from a rear well of a harvester unit, or thelike.

[0076] A practical application of these observations has already beensuggested in FIG. 1 of the present application in that the cleaning mill20 is provided with an integral graff receiving unit 21. This is sizedto receive the entire contents of a delivery truck, which canconsequently dump its entire load of graff through its open tailgate(which may be hinged at the top or bottom to allow it to be swung out ofthe way). As will be apparent from the following description ofpreferred versions of the cleaning mill described below, the receivingunit is specially designed to raise the deposited graff to an elevatedentrance of the cleaning mill without encountering problems caused bythe poor flow characteristics of the graff.

[0077] Thus, an important aspect of the present invention is to avoidthe need for temporary storage of the graff by allowing for a full loadof graff from at least one delivery vehicle to be delivered at once to agraff receiving unit of a cleaning mill, which unit can then deliver aregular supply of the graff to an elevated input opening of a cleaningmill. If this is done, and if the rate of cleaning of the graff in thecleaning mill is sufficiently rapid, the graff may be transferred fromthe harvesting unit, directly to the delivery vehicle and then directlyto the cleaning mill without any intermediate storage of any kind, thusavoiding problems encountered with the use of conventional storage silosand the like. Temporary storage may of course be provided by thedelivery vehicles themselves, in that if the harvesting rate were toexceed the cleaning rate temporarily, the temporary excess of graffcould be held in a sufficient number of delivery vehicles, if needed,and provided such vehicles were available. Clearly this is to be avoidedif possible, but could provide a temporary solution to overflowproblems.

[0078] Another important aspect involves the design of the harvestingunit to make best use of the principles of graff flow described above.

[0079] Yet another important aspect of the invention involves the designof the cleaning mill that makes efficient use of movement and separationof graff, at least in part by the use of air currents.

[0080] Yet another important aspect of the invention involves the designof the harvester unit that allows it to be towed by a conventionalvehicle, e.g. a tractor. While this has nothing to do with the flowproperties of graff itself, it is important for the overall economy ofthe present invention as such vehicles tend to be less expensive tomanufacture and to operate. A special hitching arm has been developedfor this purpose.

[0081] With these basic concepts in mind, a description of preferredembodiments of the novel components of the graff harvesting system ofthe invention will be provided below.

Improved Graff-Harvesting Harvesting Unit

[0082] For even greater efficiency and effectiveness of harvesting,improved harvesting units have been developed according to the presentinvention. These harvesting units may be used in the harvesting methodindicated above or in other harvesting methods, e.g. as disclosed inU.S. Pat. No. 5,873,226.

[0083] Various graff-harvesting harvesting units are disclosed in U.S.Pat. No. 5,794,423. These harvesting units are effective, but they areexpensive to manufacture and can be cumbersome and difficult to operate.Moreover, because of the difficulties in making graff flow evenly, thematerial flow through the known harvesting units may not always beoptimum. The preferred harvesting unit of the present inventionovercomes these problems to a desirable extent.

[0084] Farmers in recent years have become used to self-propelledharvesting units, such as conventional combine harvesters. Several ofthe harvesting units disclosed in U.S. Pat. No. 5,794,423 are of theself-propelled kind. However, the required motor, driving controls andsteering mechanisms add considerably to the cost of such vehicles. U.S.Pat. No. 5,794,423 also discloses non-powered (pull-type) harvestingunits (see, for example, FIGS. 4 to 10 of the patent), but these are ofthe “wrap-around” kind, i.e. the harvesting header is positioned infront of a propulsion unit (tractor), while the remainder of theharvesting unit is positioned to the side or rear of the propulsionunit. This leads to a mechanically complicated, cumbersome and expensivedesigns.

[0085] The harvesting unit of the present invention is based in part onthe concept of providing a pull-type unit for cost-reduction (mostfarmers already have their own tractors or other suitable propulsionunits) while avoiding the complexity of the wrap-around design by towingthe harvesting unit at the rear of the propulsion unit. However, thiscreates a problem in that, if the harvesting unit is towed behind atractor, there is difficulty in providing a suitable means of attachmentbetween the two since the harvesting header (particularly a direct-cutheader) is necessarily positioned immediately behind the tractor hitchpoint, making a conventional tow bar impossible to use and blockingaccess to the tractor's mechanical and hydraulic power supplies. Theheader also has a cutter bar that must be raised, and this imposes afurther constraint on any towing system. This difficulty has beenovercome according to the present invention by providing a harvestingunit having a novel hitching arm.

[0086] A first preferred embodiment of the improved harvesting unit 15is shown in perspective view in FIG. 2 of the accompanying drawings. Asshown, the harvesting unit 15 comprises a harvesting header 30, that maybe of either the direct-cut type (e.g. a conventional header, normally7.3 to 9 m (24 to 30 feet wide)) or a swath pick-up header (normally4.25 m (14 feet) wide). A crop feeder housing 31, e.g. a chain feeder,feeds the cut crop rearwardly to the harvester body containing theunit's internal threshing mechanism, described in more detail later,where the cut crop is separated into stalks (which are returned to thefield as straw) and graff (a mixture of grain, chaff and weed seeds,etc.). The body of the harvester unit also contains a graff holdingcontainer or tank 33 to which graff is transferred after being collectedfrom the threshing mechanism. When the tank 33 is full, the unit 15 isstopped (or unloaded on-the-move), and the graff is transferred to atransport vehicle 17 (not shown in this view, but see FIG. 1) via anunloading auger 34. The harvesting unit 15 is pulled on unpowered wheels32 by a conventional tractor 16 (not shown in this view, but see FIGS. 1and 3) via a hitching arm 35 that not only acts as a tow bar, but alsosupplies mechanical and hydraulic or pneumatic power to the harvestingunit 15 from the tractor and provides a steering function.

[0087] In the harvesting unit of the invention, at least in preferredforms, several factors combine to make the use of the illustratedhitching arm possible. Unlike a regular combine harvester, theharvesting unit does not contain a grain cleaning apparatus (because itis intended to harvest graft), which means that the threshing cylinder30 may be positioned closer to the ground. The grain feeder housing 31from the cutter head to the threshing cylinder may also be made quiteshort as a result (e.g. about 1.2 m (four feet)), and this allows theharvester to be located closer to the tractor, and means that the cutterhead does not have to be raised very much in the stowed condition. Inconsequence, the hitching arm 35 may be quite short and the cutter head30 easily fits within the “crook” of the hitching arm in the raisedcondition.

[0088] In a first embodiment, the hitching arm 35 has a closed-in hollowtubular design and, in side view, as best shown in FIG. 3, it has acentrally-raised shape (referred to for convenience in the following asan “inverted U-shape”, although it is realized that this is a very loosedescription a more accurate description would be that the hitching armis elongate with two opposite ends; the arm ramps or rises upwardly fromeach end towards the centre of the arm, and the arm has a short,elevated, generally horizontal section between the ramped or raisedsections at in the middle of the arm). The inverted U-shape allows thecrook C (upward bend) of the hitching arm to extend over the top of theharvesting header 30, with enough clearance to allow the header to beraised to the elevated (stowed) position shown in FIG. 3. This generallymeans that the crook C, at its highest point, must be elevated by adistance of at least 3 m (10 feet) from the ground. The length of thehitching arm 35 must also be suitable to prevent it fouling theharvesting header 30 during normal harvesting, even when the harvestingunit 15 is steered out of direct alignment with the tractor 16 (as willbe explained later). This usually means that the hitching arm mustproject horizontally by at least about 6.5 m (21 feet). However, thehitching arm should preferably be no longer than necessary to achievethis objective in order to minimize turning moments (that may overwhelmthe steering mechanism of the tractor if they become too great) when thehitching arm is moved to one side of the tractor or the other. Forcomparison, a hitch that would have to be used for a pull-type combineharvester would have to be longer and stronger, i.e. at least 10 m (33feet) in length, because of the added weight of the combine. This makesit extremely difficult or impossible to control side forces in anon-aligned cutting operation. The maneuverability would therefore belost with such a machine.

[0089] Since the hitching arm must pull quite a heavy load (theharvesting unit plus harvested graft), and since it is of invertedapproximately U-shape as shown, forces encountered during harvestingwill tend to pull the ends 37 and 38 of the hitching arm towards or awayfrom each other. The hitching arm should therefore be made sufficientlystrong and rigid that significant flexing of this kind is prevented. Inthe illustrated embodiment, the hitching arm is made of three maintubular elements of square cross-section, 36, 39 and 40, that are weldedtogether at their interconnecting joints 41 and 42. A heavy gauge steelbox construction is suitable for this purpose.

[0090] The hitching arm 35 is shown in isolation and in longitudinalcross-section in FIG. 4. The interior 44 of the hitching arm 35 forms anenclosed channel which may be used, if desired, to accommodate hydraulicand electrical lines (not shown) extending between the tractor and theharvesting unit. Generally, the hydraulic system includes threehydraulic sets, one for pivoting the header 30, one for turning theheader, and the third for raising the header. The hydraulic cylinder 69used for raising and lowering the harvester head is visible in FIG. 3.

[0091] The top edge of the arm is used for guiding a mechanicaldriveline 45 that conveys rotary motion from the tractor's mechanicaldrive to the harvesting unit where it is used to drive the harvestingheader 30 and other components. The driveline consists of severalstraight shafts 46, 47, 48, 49, 50 interconnected at their ends by meansof constant velocity joints 51, 52, 53, 54 and 55. Alternatively, thejoints may be interlaced pairs of U-joints. The ends of the drivelinemay also include constant velocity joints 56, 57 for connection to themechanism of the harvesting unit and the tractor, respectively. Suitablebearings 58, 59, 60, 61, 62, 63, 64, 65 are provided on the uppersurface of the hitching arm to secure the driveline and to ensure thatthe shafts rotate smoothly. The constant velocity joints employed forthis purpose are preferably capable of operating at angles up to 17° andof handling power transmission of up to 150 kW (200 hp). The use ofconstant velocity joints in the driveline not only means that thedriveline may follow the inverted U-shape of the hitching arm 35, butalso (because of the constant velocity joints 56, 57 at the extreme endsof the driveline) makes it possible that the hitch arm may be moved outof direct alignment with the tractor or the harvesting unit withoutdamaging the mechanism.

[0092] The driveline may be enclosed by an elongated cover 68 (shown inpart in FIG. 2) in the form of an inverted channel section that fitsover the upper edge of the hitching arm.

[0093] As shown in FIG. 5, the hitching arm 35 is connected to a drawbar70 of the tractor 16 via a conventional hitch 71. At the opposite end,the hitching arm 35 is connected to the harvester unit 15 via a“hydra-swing” hitch, which includes a pair of hydraulic cylinders 72 and73, attached to the body of the harvester unit 15, that allow thehitching arm 35 to be kept in direct alignment with the tractor 16, ormoved to one side or the other, as shown. This sideways movement, whichcan be controlled by the operator of the tractor, allows the tractoritself to remain largely clear of the unharvested crop, and allows theharvesting unit to be swung from one side of the tractor to the other tofacilitate back-and-forth harvesting of the crop. On the other hand, bypositioning the harvesting unit directly in line with the tractor, theoverall width of the equipment may be minimized (for passing throughgates, and the like).

[0094] At its opposite end, the hitching arm 35 is connected to a frameelement 74 of the harvesting unit for rotation about a generallyvertical axis by means of a vertical pivots 75 (see FIG. 2). This allowsthe harvesting unit 15 to remain in a forward-facing direction, i.e.facing in the same direction as the tractor, when moved to one side orthe other out of direct rearward alignment with the tractor. Theunpowered wheels 32 on which the harvesting unit 15 rides are notsteerable, and these wheels tend to keep the harvesting unit moving inthe same direction as the tractor, even when the harvesting unit ismoved to one side of the tractor or the other.

[0095] As will be appreciated, the tractor 16 both powers and maneuversthe harvesting unit 15. For most applications, a standard 125 kW (165horse power (hp)) tractor with a 95 kW (125 hp) power take off (PTO)with three hydraulic couplings and suitable transmission speeds will besuitable to operate the harvesting unit 15.

[0096] As mentioned earlier, graff has proven to be an extremelydifficult material to handle because it does not flow easily and becauseit is bulky and is produced in large amounts. The threshing and storagemechanism of the illustrated harvesting unit 15 is intended to overcomethe difficulty of collecting and processing of graff.

[0097] As shown in FIG. 3, a chain-type crop feeder housing 31 conveyscut crop material into the interior of the harvesting unit 15 where thecrop material encounters a rotating threshing cylinder 77 and aperforated concave 78 that, in conjunction with a rear flanged beaterroll 79, subject the crop material to a severe threshing action. Theseparated grain, chaff and weed seeds (i.e. graff) fall through theperforated concave 78 and collect on an auger bed 80, i.e. an inner flatsurface of the harvesting unit beneath the concave provided with severalnarrow augers extending front to back. The rest of the crop (stalks andremaining grain, etc.) is then passed from the cylinder 77 to anarrangement of straw walkers 82 which separate any remaining graff fromthe stalks. The graff separated in this way also falls onto the augerbed 80. In the harvester unit 15 of the present invention, the feederhouse 31 and straw walkers 82 may be made considerably shorter thanthose used in a conventional combine harvester (e.g. only 1.2 m (4 feet)long for the feeder house, and 1.8 m (6 feet) long for the strawwalkers, as opposed to 3 m (10 feet) in a combine harvester). Thisallows a more compact unit to be constructed, and the short feederhousing 31 allows the cutter bar of the header to fit under the crook Cof the hitching arm when in the raised position. The threshing cylinder77 is also very low, i.e. much closer to the crop than in conventionalharvester designs. This allows the hitching arm 15 to be made quiteshort (e.g. 6.5 m (21 feet)). The shorter length makes possible theunique shape of the hitching arm and, in turn, the unique shape makes itpossible for the header to be raised and lowered inside the crook of thehitching arm.

[0098] The stalks are moved by the straw walkers to the rear of theharvesting unit 15, where they are discharged onto the ground through adischarge opening 83 either as a swath or as small pieces formed whenthe stalks encounter an optional straw chopper/spreader 84. As noted,the graff separated by the straw walkers 82 falls through the strawwalkers to the bed 80 of the harvesting unit.

[0099] The threshing and graff collection section of the harvester unit15 is shown in isolation and increased size in FIG. 3A, in particularshowing the various pulleys and drive belts and chains. The feeder ofthe feeder housing 31 is driven by feeder drive belt 180, and thecylinder 77 is driven by cylinder drive belt 181. Element 182 is avariable drive belt driven by the main pulley 183. The beater 79 isdriven by a beater drive belt 184, and chopper 84 is driven by chopperdrive belt 185. A secondary counter shaft 186 is driven by a secondaryshaft drive belt 187. The straw walkers 82 and auger bed 80 are drivenby drive belt 188. Element 189 is a conveyor drive chain.

[0100] The auger bed 80 is shown in plan view of FIG. 6 in isolationfrom the other elements of the harvesting unit. The bed 80 slopesupwardly slightly from front to rear, but the graff, as it collects, ismoved from below towards the rear of the bed by a set of severalrotating augers 84 provided just above the surface of the bed 80 andorientated in parallel from the front of the bed to the back and acrossthe entire width of the bed. The graff is thus moved bodily towards therear and encounters a transverse channel 85 containing a pair of coaxialcross augers 86, 87 that move the graff in opposite outward directionsshown by arrows A and B towards vertical paddle elevators 88, 89. Thestorage tank 33 of the harvesting unit 15 (see FIG. 2) is positionedimmediately above the collection bed 80 with enough vertical clearancefor the augers 84 and the collected graff.

[0101] It is to be noted that, unlike many combine harvesters, theharvesting unit 15 lacks grain cleaning apparatus and a mechanism forreturning unthreshed heads to the threshing cylinder. This makes itpossible to design a harvesting unit having a low profile because thestorage tank 33 may sit low over the auger bed 80, and it also resultsin a power saving since material is not being recirculated through thethreshing mechanism. This further simplifies the harvesting unit of thepresent invention and makes it mechanically more reliable than aconventional combine harvester. In the apparatus of the invention,unthreshed heads are collected with the graff and become part of themillings, as described later.

[0102] As noted, the graff from the auger bed 80 is elevated to theheight of the top of the storage tank 33 by a pair of paddle elevators88 and 89 (see FIG. 3 and FIG. 6) for the graff located at the ends ofthe trough 85 on each side of the storage tank 33. FIGS. 7A, 7B, 7C and7C are diagrams showing how the graff is raised into the tank 33, movedtherein and removed therefrom. As shown in FIGS. 7A and 7B, the graffelevators 88 and 89 are positioned on the outside of the unit at theirbottom ends and they extend upwardly and forwardly. The fact that twoelevators 88 and 89 are provided means that a large volume of graff fromthe collection bed 80 can be accommodated at opposite sides of the tank,ensuring a regular flow of graff from the collection bed and into thestorage tank at opposite sides, as shown by the arrows in FIG. 7A. At apoint midway between the lower and upper ends, the elevators pass insidethe tank 33, the entrance areas being shown by shading in the drawing.The elevators discharge within the tank 33 at the upper front end. Apair of inwardly-directed augers 81 move the graff to the middle of thetank where another auger 90 is provided to help distribute the materialto the rear.

[0103]FIG. 7C shows the inside of the storage tank 33 at a point behindthe elevators 88, 89. The tank has a unique shape designed to minimizeproblems caused by the poor ability of graff to flow. Various augers areprovided to keep the graff moving as required within the tank. The tankis provided with a horizontal leveling auger 90 at the top to move thegraff backwards and to prevent the formation of a central peak. A pairof rotating agitators 91, 92 are provided lower in the tank to helpprevent bridging within the body of graff. These agitators are generallyhorizontal but slope slightly upwardly towards the rear as shown in FIG.3. At the bottom of the tank 33, a pair of delivery augers 94, 95 areprovided to move the bulk of the graff rearwards towards a well 96 (seeFIG. 7D), i.e. a deeper section of the tank, formed at the rear of thetank (see FIG. 3). The lower wall 190 of the tank 33 is in the form ofan inverted V so that the graff is directed toward transport augers 94and 95. The well 96 forms the lowest collection point for the graff andis thus the last section of the tank to be emptied by an unloading auger34, the bottom end of which is positioned at the bottom of the well 96.The auger 34 is actually made up of two co-operating augers, i.e. avertical auger positioned in the well 96 that lifts the graff out of thewell 96 and a horizontal auger that moves the graff to downward facing,preferably flexible, delivery spout 97. The well 96 forms a hopper whichcontains an exposed inclined section of flighting 99 which draws graffinto the vertical, then horizontal, sections of the unloading auger. Theunloading auger may be centred along the top of the storage tank 33during harvesting, and may be swung to either side or to the rear fordischarge of the graff into a waiting vehicle 17. The unloading augersarc preferably of large diameter compared to those for unloading grainfrom combine harvesters. For example, the vertical auger may have adiameter of 41 cm (16 inches) or more and the horizontal auger may havea diameter of 35.5 cm (14 inches) or more. This allows for a very rapidemptying of the tank, i.e. in the region of three minutes.

[0104] All of the various augers and agitators are driven by mechanicaltransmissions (e.g. belts and pulleys) taking power from the rotatingshaft carried by the hitching arm 35.

[0105] The storage tank 33, which is preferably of approximately 21 m3(750 cubic feet) in capacity (at least twice the size of the collectionbin of the largest conventional combine harvester) and (as noted above)preferably has the same size as a truck box of the vehicle 17, ispreferably provided with a particular shape that facilitates the storageand movement of the graff. As shown in FIGS. 7A, 7B, 7C and 7D, thefront wall 27 and lower parts of the side walls 28, 29 of the tank slopeinwardly from the top to the bottom. The angle of slope is preferablymade at least 50° relative to the horizontal, so that the graff slidestowards the bottom of the tank and does not become trapped at the baseof the front and side walls in the form of stagnant piles. This featuremakes use of the observed ability of graff to slide freely down a slopehaving a suitable angle of inclination. The sloping front wall 27 alsoallows the tank to clear the hitching arm 35 and allows better weightdistribution.

[0106] Although the storage tank 33 is designed to hold a substantialamount of graff, the low density of this material means that the tankdoes not have to be unusually strong, so there is no need forcross-bracing of the walls, or the like. In fact, the sculptured(tapering) shape of the tank increases its structural strength relativeto a rectangular tank of the same capacity.

[0107] The tank preferably has an open hatch 98 (FIG. 7C) on the topsurface that may be covered when desired by a roll-back tarpaulin (notshown) or the like. This allows access to the interior of the tank formaintenance and to clear blockages.

[0108] It has been found advantageous to coat the inside of the tank 33and auger chutes with a paint that forms a low friction surface in orderto minimize binding of the graff at the sides of the tank. Preferably,the paint should provide a surface having a co-efficient of friction ofless than about 0.45. Paint containing powdered graphite (e.g. paintsold by Acu Mech Sys Enterprises Ltd., under the trademark SLIP-PLATE®)is particularly effective in this way.

[0109]FIG. 8 is a side view of an alternative preferred embodiment ofthe harvesting unit and hitching arm of the present invention. In thedescription of this embodiment, elements that are identical orequivalent to those of the previous embodiment are identified by thesame reference number with an added prime (e.g. 15 becomes 15′).

[0110] It will first of all be noted from FIG. 8 that the hitching arm35′ is made up of four sections rather than three, these sections being36′, 39′, 40′ and an additional vertical section 39 a at the tractor endof the hitching arm. The presence of the additional section gives thearm a greater approximation to the inverted U-shape mentioned earlierand provides greater “headroom” C′ above the harvesting header 30′ toallow the header to be raised fully to the inactive position, and alsoallows more room for the harvesting header in the operational positionduring swinging of the harvester unit 15′ out from one side of thetractor 16′ or the other. Depending on the materials of construction,this embodiment may encounter slightly more flexing during use than thehitching arm of the previous embodiment, the total amount of flexingbeing about 0.3 m (1 foot) between the opposite ends, and so this degreeof flexing must be accommodated by the mechanical drive line 45′. Thiscan best be done by providing U-joints at the points where the driveline bends to follow the shape of the hitching arm, and also byproviding slip joints (splined telescopic sections) within the drivelineitself to accommodate lengthening and shortening actions of the line. Asa alternative to using U-joints for this purpose, it is also possible touse gearbox designs to achieve the required change of angle. A suitablegearbox design is shown in enlarged partial section in FIG. 8A, whichshows the driveline 45′ at the junction of arm sections 36′ and 39′. Thegearbox 801 consists of a housing 802 containing mutually-meshingrotatable beveled gears 803 and 804. The lowermost gear 804 is attachedto driveline section 47′ for rotation therewith and the uppermost gearis attached to driveline section 48′ for rotation therewith. The angleat which the gears are mutually arranged creates the change of directionof the driveline 45′ as it passes through the gearbox 801. A smalldegree of angular misalignment of the gears 803 and 804 is possible toaccommodate flexing, and more is permitted by the presence of constantvelocity joint 805 on one side of the gearbox and a slip joint 806 onthe other side. The gearbox must be strong enough to transmit the powerprovided to the driveline 45′ without distortion or overheating.

[0111] At the point of attachment of the hitching arm 35′ to the tractor16′, a ball joint 807 is provided to allow sharp turns, and a gearbox808 may be bolted to the tractor body.

[0112] In this embodiment, the hitching arm 35′ is attached to theharvesting unit 15′ at pivot 75′ which is placed no more than about 1.2m (4 feet) in front of the rotational axis of the wheels 32′. Thispositioning is important for two reasons. Firstly, the close proximityof the pivot 75′ to the wheels means that easier turning of theharvesting unit by the hydraulic cylinders 72′ and 73′ (See FIG. 8C) canbe achieved. Secondly, the centre of gravity of the harvesting unit isslightly to the front of the wheels when the unit is empty, but movesrearwardly of the wheels as the unit is filled during harvesting. Thisreduces the downward force on the hitching arm and allows the hitchingarm to be of a lighter design than would otherwise be the case.

[0113] In this embodiment, the hydraulic lines from the tractor 16′ tothe harvesting unit 15′ preferably follow the outside of the hitchingarm 35′ (rather than run through the hollow interior) for easierservicing, and the clearance of the cylinder can be adjusted from insidethe tractor (along with all of the other hydraulic functions, preferablyusing a single-handed joystick design).

[0114] The harvesting unit 15′ of FIG. 8 differs from the harvestingunit 15 previously described in several respects, as described in thefollowing.

[0115] Firstly, instead of equipping the floor of the tank 33′ with aseries of parallel augers, as in the previous embodiment, in order tomove the collected graff towards the rear of the tank, a “live floor”810 is provided, i.e. an endless belt made up, for example, of mutuallyspaced transverse slats driven by chains. This makes use of theprincipal mentioned earlier that graff may be moved by moving orremoving the entire lowermost layer of a body of the graff, i.e. alowermost layer that extends completely across the width of the body ofgraff—in this case substantially the entire width of the tank 33′. Inthe previous embodiment, the intention was to deliver the graff asquickly as possible to a large rear well 96 positioned at the rear ofthe tank 33 from which the graff can be augered out as shown in FIG. 7D.In this second embodiment, the approach taken to graff removal isdifferent. Instead of the large well 96, the tank 33′ is provided with ashallow transverse well or channel 96′ enclosing a quite large (e.g. 50to 60 cm (20 or 24 inches)) generally horizontal transverse auger 820 oralternatively a conveyor belt). The live floor 810 slopes upwardly tothe rear and thus the bulk of the body of collected graff tends toremain towards the front of the tank 33′ and the movement of the livefloor feeds a constant supply of graff into the channel 96′ when theauger is operated, thus reducing the risk that binding will take placeabove the auger, or blockage of the channel 96′ will occur.

[0116] The slats circulate around a plate 811 acting as a false floor ofthe tank and the slats themselves may be provided with flexible stripsat the front to provide a sweeping action over the false floor. Thechains 812 used to drive the slats (generally there are at least 2 andpreferably 3 parallel chains) provide an open structure that isself-cleaning as it moves around the false floor. An alternativepossibility would be to use a flexible (e.g. rubber) conveyor beltinstead of the slats and chains, but material tends to build upunderneath such arrangements, so they are usable but no preferred.

[0117] The transverse auger 820 in the channel 96′ feeds a side-mountedhinged enclosed conveyor 815 or chute that is used to transfer thecollected graff to an adjacent vehicle (not shown). The fact that theconveyor 815 is hinged means that it can be raised or lowered to a pointjust above the vehicle box. A conveyor is used rather than an auger toprovide bodily transport of the graff supplied by the auger to preventbinding and blockage. The arrangement also allows the tank to be emptiedquickly, e.g. within about 3 minutes or less.

[0118] A pair of augers 817 and 818 are provided at the top of the tank33′ in order to level the pile of graff (not shown) collected in thetank. These help to move the body of collected graff towards the rear ofthe tank. A sensor (not shown) is provided to indicate when the tank 33′is full so that graff does not overflow into and build up above thechannel 96′ before the auger 820 can be operated to begin removal of thegraff from the tank. Such overfilling could promote binding andblockage. The harvesting is interrupted when the sensor indicates thatthe tank is full and emptying commences, assuming that emptying is notbeing carried out simultaneously with harvesting (i.e. into a movingaccompanying vehicle).

[0119] In this embodiment, the tank may be made larger than the previousembodiment and the slope of side walls 28′ and 29′ is made a minimum of60°. The interior of the tank is again coated with low friction paint.The increased capacity may be obtained by increasing the height of theunit to 4.25 m (14 feet) and increasing its length (e.g. byapproximately 1.5 m (5 feet)). This may result in a tank 33′ having avolume of approximately 31.8 m³ (1120 cubic feet). While the tank 33′ isgenerally made of sheet metal, such as steel, the tank may,alternatively, be made of plastic material as the graff load is lightdespite the large volume.

Cleaning Mill

[0120] To further improve the efficiency and effectiveness of theharvesting method, an improved cleaning mill 20 (often referred to as ayard plant) has been produced.

[0121] The cleaning mill 20 is illustrated in perspective view in FIG.9, from which it can be seen that the mill consists of several mainparts, namely a drive-in graff receiving unit 21 (which acts as an openreceptacle for the graff delivered by a vehicle) and graff conveyor 100,an aspirator 101 for removing chaff and light material from the graff, amillings collection unit 102, a screening unit 103, and a rolling mill104. The aspirator 101 is powered by a Written Pole motor 105, oralternatively a diesel motor, and the mill is controlled by a computermodule 106 (PLC).

[0122] Graff is delivered to the cleaning mill 20 directly from thefield by a truck 17 (see FIG. 1). In the past, attempts were made topour the graff through a small door positioned in the rear wall or gateof the truck box in the same manner that grain is delivered to a grainstorage area. However, as noted above, graff does not flow in the sameway as grain, and once deposited in a pile, it is difficult to pick upand convey to the cleaning mill. To overcome this problem, theillustrated cleaning mill has a drive-in graff receiving unit 21 thatallows a truck to back directly into the receptacle (as suggested by thetire tracks 107 shown in FIG. 9) and to dump the graff by unhooking therear gate and raising the truck box (as illustrated in FIG. 1).

[0123] The graff receiving unit 21 is a grain receptacle in the form ofa flat box 108 having a slightly ramped bottom wall 109 and twolongitudinal side walls 1 10, but no end walls. The unit is aligned withthe more steeply upwardly ramped graff feeding apparatus or conveyor 100forming an inclined surface. FIGS. 11 and 12 are side views showing thereceiving unit in a receiving position (FIG. 11) awaiting a graffdelivery, and in the upturned operational position (FIG. 12), in whichthe receiving unit acts as a chute so that graff is urged onto thebottom end of the graff conveyor 100. The tilting of the receiving unitis controlled by hydraulic cylinders on each side of the unit (althoughonly one is shown in FIGS. 11 and 12).

[0124] In the case of the graff conveyor, the ramped surface 113 isprovided with a rotating drag chain conveyor 112 that moves up the rampand carries graff to the upper end 114. A rotating delivery roller 115at the upper end of the drag chain conveyor functions to beat back graffcoming up the conveyor and equalize out the graff across the width ofthe box (usually 10 feet wide) so that only a 4 to 8 cm (1.5 inch to 3inch) mat of graff proceeds to the top 114 of the graff receiving unit.The thickness of the mat is determined by the adjustable distance fromthe drag chain 112 to the roller 115. The roller is positioned a shortdistance (a few centimetres) above the upper end of the ramped surface113, and is provided with projecting teeth 116 spaced along and aroundthe circumference of the roller. The delivery roller is rotated rapidlyby a motor (not shown) and, as noted, feeds a “mat” or carpet of graff(i.e. a continuous strip of even width and thickness) into an upperentrance 117 of the aspirator unit 101 (see FIG. 9). The graff conveyor100 serves the purpose of lifting the graff from ground level to anelevated position from which it may be subjected to aspiration as itfalls vertically back to ground level within the cleaning mill. A secondfunction of the drag chain conveyor 112 is to meter (by changing thespeed of the conveyor driven by a variable speed motor) the correctvolume of graff delivered to the top 114 of the receiving unit and intothe aspirator 101. Therefore, by varying the speed of the conveyor andby varying the distance between it and the roller 115, acceptableamounts of graff can be metered into the aspirator 101. It is importantthat the entire width of the aspirator (3 m (10 feet) for 91,000 litres(2,500 bushels) per hour) is matched to the width of the receiving unitto facilitate the continuous material flow capability of the entiremachine.

[0125] The aspirator 101 is shown in greater detail and in isolationfrom the other equipment in 30 FIG. 13A, 13B and 13C. The mat or carpetof graff passes through an entrance 117 to the aspirator unit anddirectly encounters an aspirator reel 300. The reel is shown inisolation in FIG. 13C and it will be seen that a number of rubber cogs301 (three inches in height) are arranged along the surface of the reelwith a slight twist (preferably about 10°) in the axial direction tofacilitate entry of the graff into the aspirator. The rubber cogs 301form an air seal preventing air under pressure in the aspirator 101 fromescaping through the inlet 117. It will be seen from FIG. 13A that thereis no free space within the entrance 117 to allow graff to settle andclog the apparatus. Once graff passes through the entrance 117, it isimmediately taken up by the reel which delivers it to the aspirator. Asa stream 118 of graff falls vertically through the aspirator, it issubjected to a lateral airflow 119 that impinges on one side (the front)of the stream and passes through to the other side carrying away chaffand other light materials. The aspirator has six drop zones defined bybaffles 120. The air flow through each drop zone is controlled by amanually adjustable damper 121 at the drop zone's inlet. In each dropzone, the air stream passes through the falling graff.

[0126] The airflow 119 is created by a fan 122 which moves air along alower duct 123 to a front end of the aspirator, and then, after passingthrough the falling stream of graff 118, returns the air (and entrainedchaff and light materials) through an upper duct 124. If too much air isentering into the front of the aspirator 101, air can be bled offdirectly into the return air flow by a manually operated gate 302. Acentrifugal (cyclone) separator 125 removes the chaff and lightmaterials from the air flow before the air returns to the fan 122. Theseparated mixture of chaff and light materials (referred to as“millings”) is conveyed by a material conveying fan 126 (see FIG. 13B)to a conveying tube 127 and may be delivered to a suitable storage pile,container, or vehicle via a pipe 128 (see FIG. 13D) attached to theconveying tube 127. The pipe 128 (which may be as long as 15 to 21 m (50to 70 feet)) has a small cyclone unit 129 at its remote end acting as adecelerator for the millings to prevent widespread distribution of thislight material, and allowing it to collect into a pile 135.

[0127] The operation of the separator cyclone 125 is governed by the fan122 (see FIG. 13A) operating at a volume of about 340 m³ (12,000 cubicfeet) per minute (for 91,000 litres (2,500 bushels) of graff per hourthroughput). The fan forces air through the aspirator 101 and along duct124 to the separator 125. The millings material contained in the airflowupon reaching the separator clings to the outer wall of the separator bycentrifugal force and moves to a final discharge portal 303. Thedischarge through portal 303 is assisted by air equalization tube 304shown in FIG. 9 and by the discharge fan 126 shown in FIG. 13B. Withinthe separator 125, clean air in the middle of the unit is returned tothe fan 122 by duct 305 shown in FIG. 13B. The cleaned air is driven bythe fan 122 and returns to the aspirator 101 via ducting 123 to a frontside of the aspirator. The ducting forms a closed loop for the air torecirculate between the centrifugal separator 125 and the aspirator 101.Dust build-up within the closed loop is avoided by the introduction ofmake-up air from the rolling mill 172 and screening unit 103.

[0128] The heavy material 130 (aspirated graff, which contains the grainand weed seeds, etc.) collects at the bottom of the aspirator 101 and isremoved by a horizontal cross auger 131, then raised by paddle elevator132 (see FIG. 9) to a drop tube 133, from which it falls into thescreening unit 103 for separation into the desired cleaned grain productand other a secondary product comprising the remaining organic material.

[0129] The screening unit 103 is shown in detail in the perspective viewof FIG. 10. The material delivered from drop tube 133 falls into a split(bi-directional) leveling auger 140 positioned at the upper end of thescreening unit which serves to distribute the material evenly across thescreens. The unit consists of an open framework 141, retaining a numberof downwardly sloping oscillating screens 142 arranged in two groups or“shoes.” The opening size of the screens decreases from the uppermost tothe lowermost screen, so that larger particles are collected on theupper screens and smaller particles descend to the lower screens. Aseparation of the aspirated graff based on particle size is thusobtained. The top shoe 143, contains three scalping screens 144, 145 and146, through which the grain passes and large material is removed. Thefirst screen 144 of this shoe directs stones and larger debris to ahopper 307 from which it exits the machine. The second and thirdscreens, through which grain kernels drop, direct larger crop materialto a trough 147. From the top shoe, the grain flow is divided anddropped onto two screens on the bottom shoe 148. The bottom shoe 148contains two sets of three inclined, oscillating sizing screens. Thegrain passes over the screens while the “screenings” (weed seeds, smallkernels, etc.) pass through and are gathered in a trough below thescreen. The grain then drops through a plenum 160 with a cross-flow airstream where dust is removed from the grain and conveyed through a dustdelivery tube 150. The grain falls into a cross-conveyor 161, whichdelivers the grain 25 into a hopper 165. From the hopper, the grain isconveyed to storage.

[0130] Screenings from the two top shoe screens and the six bottom shoescreens are gathered in troughs and routed via drop tubes to the bottomshoes screenings collection trough. From this trough, the screenings aredelivered into a paddle elevator 170, which lifts the screenings to adrop tube 171, from which the screenings fall into an intake hopper of arolling mill 172 (see FIG. 9) where the screenings are rolled. From thebottom of the rolling mill 172, air is drawn along with the rolledscreenings into a duct 308 connected to an intake 309 of the cycloneseparator 102. Within the separator 125, the rolled screenings from themill 172 are re-combined with the light material from the aspirator 101and the dust from the plenum 160 of the screening unit 103 delivered viadust delivery tube 150.

[0131] As already noted, solids (millings) separated from the air byseparator 125 are drawn by a portion of the air through a duct 173 intoa material-conveying fan 126 (FIG. 13B). The fan helps to remove themillings and air from the separator 125 in a continuous manner withoutdisrupting the centrifugal separation effect within the separator. Thishas proven to be in improvement on the usual air lock provided forremoval of solids from a separator. The fan 125 also makes it possibleto project the millings a considerable distance from the machine viaconveying tube 127 and pipe 128 to the small cyclone decelerator 129.The millings, which consist of just about all of the organic matter fromthe graff other than the grain kernels are dropped into a pile 135 forstorage. Weed seeds in this material have been passed through therolling mill 172 and thus are no longer viable (i.e. they are inert).Moreover, small screened grain kernels are also crushed, making themmore digestible for cattle. The collected millings are therefore avaluable product that may be used as animal feed or for other purposes.Despite this rolling step, only a single material (other than thecleaned grain) is discharged from the mill because of the recirculationof rolled material to the intake of the separator unit where it is mixedwith light materials from the aspirator. Of note is also the final airbath applied to the cleaned grain just before it is discharged from themill. This air bath removes fine dust that is also recirculated to theintake of the separator 125.

[0132] Of course, if desired, the rolled material and/or the dust fromthe air bath need not be returned to the separator, but could bedischarged independently merely by rerouting the indicated piping. Thematerial from the screens (screenings) is by itself a high protein feedmaterial.

[0133] A particular advantage of the cleaning mill is that, if desired,it can be operated automatically, essentially without an operator.Computer control ensures normal operation of the mill at all times.

[0134] An alternative embodiment of the cleaning mill is shown in FIGS.14 and 15. In this embodiment, the graff receiving unit 21′ (which formsan open receptacle for the graff) and the graff conveyor 100′ areessentially the same as in the previous embodiment and allow graff to bedeposited as a full load from a truck by upending the truck box, dumpingthe graff load, and delivered in a constant stream to a laterallyelongated upper inlet 117′ of the cleaning mill without binding orblocking and without the need for intermediate storage. However, uponpassing through the inlet 117′, the graff enters a transverse channel900 containing a cross-directed gathering auger 901 (which preferablyhas a diameter of 43 cm (17 inch)). The purpose of this auger is toreduce the width of the graff flow from that of the graff conveyor 100′(approximately 3 m or 3.3 m (10 or 11 feet)) to that of the width of thecleaning mill itself, which is somewhat narrower (approximately 143 cm(56 inches)). By this means, the both the cleaning mill and the conveyormay be designed to have optimal widths for their intended functions,even though those widths may differ.

[0135] In this embodiment, the screening unit 103 of the previousembodiment is incorporated into the main body 905 of the cleaning mill20′. This makes the cleaning mill more compact and easier to operate. Asshown in simplified schematic form in FIG. 14, upon leaving thetransverse channel 900 at the central opening 975, the graff falls ontoa grain pan 907 provided with a reciprocating action that tends tostratify the graff into components of different density and levels thegraff into an even carpet 908 having a width of 0.6 to 1.2 m (2 to 4feet). The grain pan moves the graff forwards until it falls onto acleaning shoe 909. The cleaning show includes an upper chaffer screen910 and a lower grain sieve 911 (both of which are of adjustable meshsize) that are reciprocated back and forth in an opposed motion. A shortextension sieve 912 is also provided at the distant end of the chaffer910. This can be adjusted independently of the chaffer, and can beraised at an angle to slow down the flow of material, if desired. Thechaffer and grain sieve each preferably have a surface area of about 1.7m² (17.9 sq. ft.). The mesh size of the chaffer is larger than that ofthe grain sieve. As the graff passes through the shoe 909, large chaff,stalks, cut heads and stones are separated mainly by the chaffer 910 andthen intermediate contents (e.g. weed seeds, small chaff, stalk parts,etc.), are separated al the grain sieve 911. Essentially only grain 915itself passes through the grain sieve 911 and falls to a collection pan916 that has sloping front and rear walls directing the grain to acentral trough 917 for removal by a cross auger 918 through a grain exit919.

[0136] As the graff is separated into its components in this way, air isblown upwardly and outwardly through the shoe 909 as indicated by arrowsA. This air flow suspends essentially all of the graff components exceptthe grain and heavy objects such as stones. In fact, as the graff dropsonto the shoe 909 from the grain pan 907, it encounters a blast of airforceful enough to blow away essentially everything but clean grainkernels of the desired size (and heavy objects, such as stones). Thisreduces the amount of separation required to be carried out by the shoe911 itself. Both the suspended chaff and the heavy objects proceed to acyclone separating unit 920. The suspended chaff is carried by the airflow, whereas the heavy objects are moved by the reciprocating action ofthe shoe sieves into the inlet 921 of the cyclone unit.

[0137] The airflow is created by a fan 925 (e.g. a 16.5 kW (22 hp)centrifugal fan creating a throughput of 400 m³/min (4,000 cubicfeet/minute)) positioned within the cleaning mill beneath the graffconveyor 100′. The fan directs air into conduit 926 leading to thecleaning shoe 909, but an adjustable diverter 927 is provided upstreamof the shoe to direct a portion of the air into a bypass conduit 930 asindicated by arrows B. The air from the bypass 930 nevertheless alsoenters the cyclone unit 920 with the air that has passed through thecleaning shoe 909. The diverter allows the airflow A through the shoe tobe made appropriate for cleaning the graff (designed to blow awayeverything below kernel removal) while still allowing a high rate ofairflow through the cyclone unit 920. The diverter 927 may be eithermanually adjustable or automatically controlled based on the rate offeed of graff into the cleaning mill.

[0138] A stone cleanout door 932 is provided at the bottom of thecyclone unit 920 to allow stones and other large or heavy objects to beremoved periodically from the bottom of the cyclone unit where they tendto collect as they are not removed by the airflow.

[0139] The cyclone unit 920, by virtue of the spiral flow of air therethrough and the density of the suspended chaff, causes the suspendedchaff to congregate around the inside wall 935 of the unit so that cleanair that is substantially free of chaff and other solids may exit theunit through a central opening 936. The chaff, propelled by a furtherflow of air, exits a chaff delivery port 937 located at an outside lowerregion of the cyclone unit. The clean air is recirculated directly tothe fan 925 via ducting 940 (see FIG. 15), although a certain amount ofclean air from the outside may be introduced into the recirculated air,e.g. through an elongated slot provided adjacent to the graff entrance117′, to replace air escaping with the chaff and to reduce the build-upof dust (about 90% recirculation is usual).

[0140] The solids exiting chaff delivery port 919 contains chaff proper,weed seeds, unthreshed heads, and small grain kernels. As shown in FIG.15, this is conveyed through ducting 950 to a high speed centrifugalmaterial-conveying fan 951 provided with paddle-like blades. The fan hasa hammering, impacting or chopping effect that reduces the size of largeitems and tends to crack, nick or crush weed seeds and small grainkernels (thus making them less liable to germinate). The fan ispreferably operated at a speed of about 3293 rpm, giving the fan avelocity at its blade tips of about 440 km/hr and a throughput of about57 m³/min (2000 cubic feet/minute). Obviously, variations (e.g. ±10%) ofthese speeds and velocities may be employed, provided the desiredmaterial conveying and seed cracking effects are obtained. The materialexiting the fan is then conveyed through tubing 952 to a desiredlocation where it is discharged to form an open pile (not shown) (or itmay, if desired, be discharged into a silo or other form of container,however the crushed millings adhere to themselves and cake together sothe material tends not to blow away from an open pile). The millingsform a good quality animal feed similar in nutrient content to hay. Thefan 951 and tubing 952 may convey the solids up to a distance of about60 m (200 feet) from the cleaning mill, depending upon the power of thefan 951. The fan 951 acts to both convey the separated solids and tocrush them. It acts at a fast rate of throughput and is rarely subjectto blockage, plugging or failure for other reasons. This is all achievedat a reasonable cost in power to operate the fan.

[0141] In a preferred form of this embodiment, as shown, a single motor955 is used to drive both the air fan 925 and the material-conveying fan951. This is preferably a written pole (single phase) electric motor of30 to 37.5 kW (40-50 hp). Approximately eight additional small electricmotors (of approximately 1.5-2.25 kW (2-3 hp) each) are required for thecomplete operation of the cleaning mill. Advantageously, all thesemotors may be designed to operate on single phase power that is mostreadily available on farms and in remote areas.

[0142] The cleaned grain exits the grain delivery port (propelled by thepositive air pressure in the cleaning mill or extracted by an auger) andis delivered by an auger to a storage container (e.g. one or moresilos—not shown).

[0143] The cleaning mill of this embodiment maintains a constantrecirculation of air and a constant stream of graff into the mill andconstant streams of cleaned grain and the remaining constituents fromthe mill. The illustrated unit is capable of processing 91,000 litres(2500 bushels) of graff per hour. The receiving unit 21′ is capable ofholding at least 27,000 litres (750 bushels) of graff. A single loadfrom a truck can therefore be processed in about 20 minutes.

[0144] The mill can be essentially left to operate without supervision.The truck operator can use a remote control device to lower thereceiving unit as the truck approaches, dump the load of graff, and thenset the cleaning mill in operation and leave for another load. The millmay be computer controlled to raise the receiving unit in stages to feedthe graff conveyor appropriately, and to run all of the fans and motorsuntil a sensor indicates that all of the graff has been processed. Theunit may then shut itself off automatically, awaiting the next load.

What I claim is:
 1. A method of harvesting and cleaning a plant crop,wherein the crop is cut from a field area and threshed in a mobileharvesting unit to produce stalks that are returned to the field areaand “graff”, a mixture including grain, chaff and weed seeds, which iscollected within the harvesting unit; the collected graff is transferredperiodically from the harvesting unit to at least one vehicle andtransported by said at least one vehicle to a cleaning mill, and thegraff is cleaned by the cleaning mill to produce a cleaned grain productand “millings”, a mixture including chaff and weed seeds; wherein themethod is operated to avoid storage of the graff prior to cleaning bysaid cleaning mill.
 2. The method of claim 1, wherein storage of thegraff prior to cleaning is avoided, at least in part, by emptying anentire graff load from said at least one vehicle by direct dumping ofthe entire graff load into a graff receiving unit of said cleaning mill,and directly feeding graff from the dumped load into a graff entrance ofthe cleaning mill at a rate at which the graff can be continuouslycleaned by the cleaning mill, until all of said load has been fed intothe cleaning unit.
 3. The method of claim 2, wherein graff is fed fromthe dumped load to the graff entrance of the cleaning mill by removinggraff from a lowermost layer of the dumped load over substantially theentire transverse width of said dumped load to avoid interruptions ofgraff feed caused by binding, blocking, or bridging of the graff withinthe load.
 4. The method of claim 3, wherein the graff is removed fromsaid lowermost layer of the dumped load by positioning the load on asurface and moving the surface, or elements extending across thesurface, beneath the load.
 5. The method of claim 4, wherein the surfaceis inclined upwardly towards the graff entrance of the cleaning mill,and the load is kept in contact with the inclined surface by raising afloor of the graff receiving unit to form a downwardly inclined chutethat urges the load against the upwardly inclined surface.
 6. The methodof claim 1, wherein storage of the graff prior to cleaning is avoided,at least in part, by making the graff holding capacity of the harvestingunit the same as or smaller than the graff holding capacity of said atleast one vehicle, so that all of said graff collected in saidharvesting unit may be transferred in a single emptying operation tosaid at least one vehicle.
 7. The method of claim 6, wherein thecapacity of the harvesting unit is made substantially the same as thecapacity of the at least one vehicle.
 8. The method of claim 1, whereinstorage of said graff prior to cleaning is avoided, at least in part, bycleaning the graff in the cleaning mill at a rate that is the same as orhigher than the rate of graff output from the field area.
 9. The methodof claim 8, wherein the rate of cleaning of the graff by the cleaningmill is substantially the same as the rate of graff output from thefield area.
 10. The method of claim 1, wherein storage of said graffprior to cleaning is avoided, at least in part, by operating said atleast one vehicle such that graff is conveyed from the harvesting unitto the cleaning mill at a rate high enough to avoid substantial waitingperiods between emptying operations of said harvester unit.
 11. Themethod of claim 1, wherein the graff is transported from the harvestingunit to the cleaning mill in a single vehicle travelling continuallyback and forth between the harvesting unit and the cleaning mill.
 12. Asystem for harvesting and cleaning a plant crop, which includes aharvesting unit for cutting a crop from a field area and threshing thecut crop to produce stalks that are returned to the field area and“graff”, a mixture including grain, chaff and weed seeds, which iscollected within the harvesting unit; at least one vehicle for receivingcollected graff from the harvester unit when the harvesting unit is atleast partially full, and for transporting the graff to a cleaning mill;and a cleaning mill located in a yard area remote from the field area,for cleaning the graff to produce a cleaned grain product and“millings”, a mixture containing chaff and weed seeds; wherein thesystem excludes any device for storage of the graff prior to cleaning ofthe graff in the cleaning mill.
 13. The system of claim 12, wherein thecleaning mill includes a graff receiving unit into which said at leastone vehicle may empty an entire graff load by dumping, the receivingunit including feeding apparatus for directly feeding graff from thedumped load into a graff entrance of the cleaning mill.
 14. The systemof claim 13, wherein the feeding apparatus removes graff from alowermost layer of the dumped graff load over substantially the entiretransverse width of the dumped load, thereby avoiding interruptionscaused by binding, blocking or bridging of the graff within the load.15. The system of claim 14, wherein the feeding apparatus includes asurface on which the load may be positioned, and means for moving thesurface, or elements extending transversely across the surface, toconvey graff from the load to the graff entrance of the cleaning mill.16. The system of claim 15, wherein the surface is inclined upwardly tothe graff entrance of the cleaning mill, and the receiving unit includesa floor that may be raised to form a downwardly inclined chute thatkeeps the load in contact with the inclined surface.
 17. The system ofclaim 15, wherein the elements extending transversely across the surfaceare mutually spaced transverse slats supported and moved towards thegraff entrance of the cleaning mill by rotating endless chains passingaround the inclined surface.
 18. The system of claim 16, wherein arotating transverse roller is provided above the inclined surface at anupper end thereof to ensure that graff fed to the graff entrance of thecleaning mill is in the form of a layer of uniform thickness.
 19. Thesystem of claim 12, wherein the harvesting unit has a graff holdingcapacity that is the same as or smaller than the graff holding capacityof said at least one vehicle used for graff transportation.
 20. Thesystem of claim 12, wherein the cleaning mill operates at a rate ofcleaning of the graff that is the same as or higher than the rate ofgraff output from the field area.
 21. The system of claim 12, whereinsaid at least one vehicle may be operated at a rate high enough toconvey graff from the harvesting unit to the cleaning mill whileavoiding substantial waiting periods between emptying operations of saidharvesting unit.
 22. The system of claim 21, wherein a single vehicle isprovided for conveying graff between the harvesting unit and thecleaning mill.
 23. A stationary cleaning mill for “graff”, a mixtureincluding grain, chaff and weed seeds, comprising an entrance for thegraff, screening apparatus for separating grain from the graff toproduce cleaned grain and “millings”, a mixture including chaff and weedseeds, and separate outlets for the cleaned grain and millings; whereinthe cleaning mill includes a receiving unit for the graff for feedingthe graff to the entrance of the graff cleaning mill, said receivingunit being sized to permit a graff delivery vehicle to drive in to thereceiving unit to transfer an entire vehicle load of graff to thereceiving unit by a direct dumping operation of the entire vehicle load.24. The cleaning mill of claim 23, wherein the receiving unit includes areceptacle for the graff load and a feed device for raising graff fromthe receptacle to the entrance of the mill.
 25. The cleaning mill ofclaim 23, wherein the mill includes a fan for blowing a stream of airthrough the graff to remove at least chaff, but not grain, a centrifugalseparator for removing the chaff from the stream of air, and ductworkfor recirculating air from the centrifugal separator to the fan.
 26. Thecleaning mill of claim 25, wherein the mill includes an aspirator forreceiving a falling curtain of graff, and ductwork for directing saidstream of air through the falling curtain of graff in the aspirator,thereby allowing a mixture of grain and weed seeds to fall to a lowerpart of the aspirator while removing chaff via said stream of air. 27.The cleaning mill of claim 26, wherein the screening apparatus includesa frame containing a series of screens, arranged one above another, ofdifferent mesh sizes suitable for separating grain from weed seeds, adelivery apparatus for delivering a mixture of grain and weed seeds fromthe lower part of the aspirator to an upper part of the frame, an outletfor cleaned grain emerging from the series of screens and an outlet forweed seeds emerging from the series of screens.
 28. The cleaning mill ofclaim 27, wherein the mill includes a milling device for crushing theweed seeds, and a delivery device for combining crushed weeds seeds withchaff removed from the graff.
 29. The cleaning mill of claim 27, whereinthe screening apparatus includes a plenum through which screened grainfalls before being discharged from the mill, the plenum includingducting for directing a flow of air through the falling screened grainto remove dust, and ducting for introducing the dust into thecentrifugal separator.
 30. The cleaning mill of claim 26, wherein saidscreening apparatus is positioned between said graff entrance and saidcentrifugal separator, and said mill includes ductwork that directs saidstream of air through said screening apparatus as graff from saidentrance is passed through the screening apparatus.
 31. The cleaningmill of claim 30, wherein said screening apparatus has an outlet forscreened graff components other than cleaned grain, and said outletfeeds said screened graff components other than cleaned grain into saidcentrifugal separator.
 32. The cleaning mill of claim 31, wherein acleaned grain outlet is provided at a lower part of said screeningapparatus to remove cleaned grain from the cleaning mill.
 33. Thecleaning mill of claim 30, wherein a material-conveying fan is providedat an outlet for said millings, said fan impacting said millings tocause at least partial crushing or breaking of weed seeds in themillings, removing said millings from the cleaning mill, and propellingsaid millings through said outlet for the millings.
 34. A stationarycleaning mill for “graff”, a mixture including grain, chaff and weedseeds, comprising an entrance for the graff, screening apparatus forseparating grain from the graff to produce cleaned grain and “millings”,a mixture including chaff and weed seeds, and separate outlets for thecleaned grain and millings; wherein the cleaning mill includes amaterial conveying fan at the outlet for the millings, saidmaterial-conveying fan impacting said millings to cause at least partialcrushing or breaking of weed seeds in the millings, removing saidmillings from the cleaning mill, and propelling said millings throughsaid outlet for the millings.
 35. The cleaning mill of claim 34, whereinsaid material-conveying fan is the only apparatus provided in thecleaning mill for impacting said weed seeds.
 36. The cleaning mill ofclaim 23, wherein ductwork is provided at said outlet for the millingsfor conveying said millings to a location at a distance from saidcleaning mill, said ductwork having a centrifugal separator at an outerend thereof to slow discharge of millings from the outer end of theductwork.
 37. A mobile harvesting unit for harvesting “graff”, a mixtureincluding grain, chaff and weed seeds, including a wheeled harvesterbody and a harvesting header at the front of the harvester body forcutting a crop from a field area, the harvester body containing athreshing unit for the cut crop for separating stalks from graff, adischarge for discharging separated stalks back to the field area, and astorage tank for storage of the separated graff, wherein the storagetank has a well at a rear of the tank, and the tank has a floor providedwith a movable surface, or elements that move over said floor, to conveygraff rearwardly in the tank to said well.
 38. The harvester unit ofclaim 37, wherein a collection bed for graff is provided beneath thethreshing unit, and the collection bed includes a transverse graffcollection trough at a rear end thereof, and a plurality of rotatableaugers for moving graff rearwardly towards the trough.
 39. The harvesterunit of claim 38, wherein the transverse graff collection trough housesa pair of co-axial augers for transferring graff to opposite lateralends of the graff collection trough, and a pair of graff elevators isprovided, one at each lateral side of the storage tank, for liftinggraff from the opposite lateral ends of the graff collection trough andtransferring the graff to the storage tank.
 40. The harvester unit ofclaim 37, wherein the storage tank includes at least one leveling augerfor spreading out graff fed into the tank from the threshing unit. 41.The harvester unit of claim 37, wherein the storage tank has a well at arear of the tank, and the tank contains at least one auger for conveyinggraff towards the well.
 42. The harvester unit of claim 37, wherein theelements that move over said floor are mutually spaced lateral slatsconnected to endless chains that rotate around said floor of the tank.43. The harvester unit of claim 37, wherein a discharge device isprovided for emptying the storage tank of graff when the tank is full,the discharge device having an elongated discharge tube that ispivotable on the harvesting unit, allowing discharge of graff to avehicle positioned at a side or rear of the harvesting unit.
 44. Theharvester unit of claim 37, wherein a discharge device is provided foremptying the storage tank of graff when the tank is full, the dischargedevice comprising an elongated enclosed chute extending laterally fromthe rear of the storage tank, said chute containing a conveyor forremoving graff from the storage tank.
 45. The harvester unit of claim44, wherein the chute is pivotable about a generally horizontal axis sothat an outer end of the chute may be raised or lowered.
 46. Theharvester unit of claim 37, wherein the storage tank has side walls thatslope inwardly and downwardly at an angle that causes graff to movetowards a bottom of the tank without substantial binding or bridging ofthe graff within the tank.
 47. The harvester unit of claim 46, wherein abottom wall of the storage tank rises to a central peak from saidsidewalls to a centre of the tank at angles that substantially preventbinding or bridging of the graff as it moves downwardly in the tank. 48.The harvester unit of claim 37, wherein the interior of the tank has alow friction surface.
 49. The harvester unit of claim 37, wherein thetank has a rear well, and the unit contains at least one auger to movegraff in the tank towards and into the well.
 50. The harvester unit ofclaim 37, wherein the tank has at least one agitator for agitating thegraff in the tank to facilitate movement of the graff.
 51. The harvesterunit of claim 37, wherein the tank has a front wall that slopes inwardlyfrom top to bottom.
 52. A receiving unit for “graff”, a mixturecontaining grain, chaff and weed seeds, for feeding graff to an entranceof a graff cleaning mill, including a receptacle for graff and aconveyor for raising graff from the receptacle to the entrance; whereinthe receptacle is sized to permit a graff delivery vehicle to drive intothe receptacle and to deposit an entire vehicle load of graff into thereceptacle by a direct dumping operation.
 53. The receiving unit ofclaim 52, wherein the receptacle for graff has a floor that is pivotedadjacent to the conveyor, so that the floor of the receptacle may beraised to tilt downwardly towards the conveyor.
 54. The receiving unitof claim 52, wherein the conveyor has an upwardly ramped floor providedwith a moving surface that conveys graff from the receptacle to theentrance.
 55. The receiving unit of claim 52, wherein the moving surfaceis provided by a plurality of mutually spaced transverse slats that aremoved across the ramped floor by rotating endless chains rotating aroundthe ramped floor.
 56. The receiving unit of claim 52, wherein a rotatingtransverse roller is provided above the moving surface at an upper endthereof to ensure that graff fed to the entrance of the cleaning mill isin the form of a layer of graff of uniform thickness.
 57. The receivingunit of claim 52, wherein the receptacle and the conveyor have raisedsides to confine the graff within the receiving unit.